Field of the Invention
The present invention relates to an optical apparatus and an image pickup apparatus, and more particularly to an optical apparatus capable of acquiring polarization information and an image pickup apparatus having the same.
Description of the Related Art
It is known that a predetermined feature of an object can be emphasized to be detected by observing a polarization state of light from the object. For example, by attaching a polarization filter (polarization plate) in front of a lens of a camera to capture an image, a texture such as a color or a contrast of the object can be emphasized or reflected light from water surface or the like can be emphasized or reduced. Furthermore, there is an inspection apparatus which detects an edge or a defect portion of an object by capturing images with different polarization directions.
As a method of acquiring an image containing polarization information, there is a method of rotating a polarization plate, but a manual operation by a user or a complicated mechanism to rotate the polarization plate is necessary. In this respect, Japanese Patent Laid-open No. 2012-80065 discloses a wire grid polarization plate through which different polarized lights for each of a plurality of pixels on a solid-state image pickup element transmit and the image pickup element which extracts polarization information from the plurality of pixels. In this configuration, a plurality of pieces of polarization information can be acquired without rotating the polarization plate. United States Patent Application Publication No. 2009/0079982 discloses a λ/4 plate, two liquid crystal wavelength plates, and a polarization plate, and it also discloses a method of acquiring a plurality of images while changing a fast axis of the wavelength plate without rotating the polarization plate.
In Japanese Patent Laid-open No. 2012-80065, the polarization information can be obtained from a single image, but resolution or color information is lost since the plurality of pixels are allocated to acquire the polarization information. In United States Patent Application Publication No. 2009/0079982, the two liquid crystal wavelength plate are necessary, and accordingly control is complicated and the cost is increased.